This project has as its objective the synthesis of carbon char microparticles for use as sensor materials in EPR and MRI oximetry. The chars are optimized for different applications and different detection techniques, including low-frequency EPR, Dynamic Nuclear Polarization (DNP), MRI and DNP-enhanced MRI. Materials are characterized in order to determine which parameters confer desired properties, such as low in vivo toxicity, chemical stability in biological environments, rapid response times, strong DNP polarization of water protons, and high unpaired spin density.